Algorithm: Looping: Post 3

Hey guys, Today we are discussing looping.
See looping is one of the most important part of programming, because almost every program uses loops.
And if you are interested in jobs related to I.T. industries then looping is one thing you need to have command on.

Some very basic questions asked during technical interview are:-
1.Draw pattern 

*****

****

***

**

*

2.Write 
                                                                             11111
                                                                             2222
                                                                             333
                                                                             44
                                                                             5



These type of questions can be done very easily if you are well acquainted with looping.

So to start with lets see what looping means 
Looping means to form loop; doing something in a loop i.e. encircling; doing something repeatedly.

So
for writing writing Hello world 5 times
we can do two thing

either go through a tiring process of writing Hello world 5 times or write in a loop

 first way 

main( )
{
           printf( "Hello world\n");
           printf( "Hello world\n");
           printf( "Hello world\n");
           printf( "Hello world\n");
           printf( "Hello world\n");
}

second way

main( )
{
     for(int i=0;i<5;i++)
     {
           printf( "Hello world\n");

      }

}

both of these program will give result

Hello world
Hello world
Hello world
Hello world
Hello world


Components of loop statement
C1>Conditions of a loop is the most important part: when should we do something
C2>What should be done if condition is fulfilled
C3>Increment or decrement part


So when you have seen what a loop do, lets see how many types of loop statements are there.
There are basically 2 types of loop statements
1. Entry control
    Here condition (C1) is checked before the first step of loop: i.e. if the condition is not fulfilled then there will be 0 steps taken     
example: for, while 

2. Exit control
Here condition (C1) is checked after the first step of loop: i.e. if the condition is not fulfilled then there will be 1 steps taken at least.
example: do while


Let us see different loop statements

For
 
    for(int i=0;i<5;i++)
    {
       print i;
     }


here execution will be like :-

• initialize i by 0
• check whether i <5
• if yes print i i.e. 0
• then do i++ i.e. i=1
• check whether i <5
• if yes print i i.e. 1
• then do i++ i.e. i=2
• check whether i <5
• if yes print i i.e. 2
• then do i++ i.e. i=3
• check whether i <5
• if yes print i i.e. 3
• then do i++ i.e. i=4
• check whether i <5
• if yes print i i.e. 4
• then do i++ i.e. i=5
• check whether i <5
• if no end the loop

now let us see two program
 1. to print 1 to 10
  main ( )
{
    int i;
    for(i=0;i<5;i++)
    {
        print("%d",i);
        print("\n");
     }
}

 this will give

0

1

2

3

4

and as per nested for loop is concerned 

 main ( )

{
    int i,j;
    for(i=1;i<=10;i++)
    {
        print("%d",i);
        print("\n");
             
           for(j=1;j<=10;j++)
             {
               print("inside loop : %d", j);
               print("/n");
              }
     }
}

this will give
1
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
2
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
3
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
4
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
5
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
6
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
7
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
8
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
9
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10
10
inside loop : 1
inside loop : 2
inside loop : 3
inside loop : 4
inside loop : 5
inside loop : 6
inside loop : 7
inside loop : 8
inside loop : 9
inside loop : 10


While

main( )
{
   int i=0;
    while(i<5)
    {
       print("%d \n",i)"
       i++;
     }
}

this will give
0
1
2
3
4

You can see it is almost like for loop

Do While

main( )
{
    int i=0;
   do
   {
     printf("%d \n",i);
     i++;
    }
    while(i<5);
}

this will give
0
1
2
3
4
5

You can see unlike other two examples (for and while) this loop statement is printing 5 also as it is checking conditions at the end.

I hope you got the zest of looping
If yes then try to reply with the answer of

1.Draw pattern 

*****

****

***

**

*

2.Write 
                                                                             11111
                                                                             2222
                                                                             333
                                                                             44
                                                                             5

OTHERWISE IN NEXT POST we will discuss answer of these and some other looping questions.